Umbilicals, such as those used subsea, and their components often need to be accessible for performance monitoring during the installation process. In many cases those same components need to be sealed from seawater ingress prior to final overboading from the installation vessel. Therefore special sealing caps, often known as abandonment caps are assembled onto the previously exposed ends of the cables.
The abandonment caps currently used use resins and oils that are problematic to transport offshore and by air due to their chemical nature, the resins also have a limited shelf life. Current products are those that utilize tapes, adhesives, resins and heatshrink sleeving, these are notoriously unreliable due to the dissimilar materials used for sealing which leave an interface for leakage. Their success also relies on the fitter's skill and attention to detail. In addition they do not facilitate testing while fitted to the cable.
Current art cables are typically manufactured with low density polyethylene conductor insulation rather than ethylene propylene copolymer (EPC) insulation. Low density polyethylene has a lower melt index making the molding process more difficult to accomplish because of washing away of the insulation and push over of conductors during the injection process. This problem would be more pronounced the smaller the conductor size.
A current cap design incorporates an epoxy resin that requires a minimum cure time of 4 hours. Therefore, for a typical umbilical with multiple MV power cores and LV cables, even when using multiple technicians assembling caps as parallel activities, the elapsed time is significant. It can easily be in excess of 12 hours per umbilical. For a project with multiple umbilicals the time taken to fit these caps represents a significant additional vessel time and therefore cost. Additionally, this process requires the umbilical to remain in a position hanging off the back of the installation vessel for those 12 hours while the caps are installed. This is not a preferred situation from the perspective of risk and fatigue accumulation in the umbilical.